Next Generation Thermoelectric Device Designs and Methods of Using Same

ABSTRACT

This patent incorporates several new modified irregular-shaped thermoelectric element designs and connections for use in thermoelectric conversion devices to increase efficiency and lower the cost and size of thermoelectric devices. Thermoelectric conversion devices using the new design criteria have demonstrated comparative higher performance than current commercially available standard thermoelectric conversion devices.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of U.S. Provisional Patent ApplicationNo. 61/459,275, entitled “Next Generation Thermoelectric Devices” filedDec. 09, 2010.

BACKGROUND Summary

Design of a thermoelectric conversion device, for power generation orcooling, of the present invention includes irregular shaped n-type andp-type thermoelectric elements. New design criteria for modified shapesand connections of thermoelectric elements are presented.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, and advantages of the designs of this inventionwill become more thoroughly apparent from the following detaileddescription, appended claims, and accompanying drawings in which theside views of typical n-type/p-type thermoelectric element pairs used inthermoelectric devices comparison testing that was performed; typicalheating and cooling (alumina) plates are mostly not depicted:

FIG. 1 is a side view of n-type/p-type thermoelectric elements thatillustrates the layout of thermoelectric elements in current typicalcommercially available thermoelectric conversion devices.

FIG. 2 illustrates the basic low-to-high area concept for athermoelectric conversion device.

FIG. 3 illustrates a thermoelectric device with both elements having thebasic low-to-high area concept and double change of heat flow directiondesign for a thermoelectric conversion device.

FIG. 4 illustrates an external thermoelectric reinforcing circuit designusing U and/or V shaped elements for a thermoelectric conversion device.

FIG. 5 illustrates a design of low-to-high area elements design with asingle change in heat flow direction incorporated for a thermoelectricdevice.

FIG. 6 illustrates a pair of thermoelectric elements including a simplelow-to-high area design and incorporating an external thermoelectricreinforcing circuit for a thermoelectric conversion device.

FIG. 7 illustrates a pair of thermoelectric elements including a simplelow-to-high area design and incorporates an open cut out at center topto integrate an external thermoelectric reinforcing circuit for athermoelectric conversion device.

FIG. 8 illustrates a pair of thermoelectric elements including a simplelow-to-high area design and incorporates an open cut out at centerbottom for a thermoelectric device.

FIG. 9 illustrates a pair of T-shaped thermoelectric elements includinga low-to-high area design and incorporating a single change of heat flowdirection with an external thermoelectric reinforcing circuit for athermoelectric conversion device.

FIGS. 10 a-10 c illustrate a pair of thermoelectric elements including asimple low-to-high area design, incorporating a cut-out to integrate anexternal thermoelectric reinforcing circuit, a double change of heatflow direction and different positions for the heat input “leg” on theelements for a thermoelectric device.

FIGS. 11 a-11 b illustrate a pair of thermoelectric elements where eachelement includes a low-to-high area design, one horizontal cut-out tooffer three changes in heat flow direction, a vertical cut-out at top tointegrate an external thermoelectric reinforcing circuit, and separatehorizontal cutout(s) at bottom of element to offer different positionsfor the heat input “leg” on the elements for a thermoelectric conversiondevice.

FIGS. 12 a-12 b illustrate a pair of thermoelectric elements where eachelement includes a simple low-to-high area design, two horizontalcutouts to offer three changes in heat flow direction, an externalthermoelectric reinforcing circuit, and different positions for the heatinput “leg” on the elements for a thermoelectric conversion device.

FIGS. 13 a-13 c illustrate a pair of thermoelectric elements where eachelement includes a simple low-to-high area design, three horizontalcutouts to offer five changes in heat flow direction, an externalthermoelectric reinforcing circuit, and different positions for the heatinput “leg” on the elements for a thermoelectric conversion device.

FIGS. 14 a-14 c illustrate a pair of thermoelectric elements, eachelement includes a simple low-to-high area design, incorporating threedeeper horizontal cutouts to offer five changes in heat flow direction,an external thermoelectric reinforcing circuit, and different positionsfor the heat input “leg” on the elements for a thermoelectric conversiondevice.

FIGS. 15 a-15 d illustrate a pair of faucet-shaped thermoelectricelements to enhance and integrate an external thermoelectric reinforcingcircuit with cutouts/holes at center to provide additional changes inheat flow direction and different positions for the heat input “leg” onthe elements for a thermoelectric conversion device.

FIG. 16 illustrates a pair of thermoelectric elements that incorporatelow-to-high area design, multiple changes of heat flow direction and anopen cutout at top to optimize workings of the external thermoelectricreinforcing circuit for a thermoelectric conversion device.

FIGS. 17 a-17 d illustrate a pair of thermoelectric elements where eachelement includes low-to-high area design, multiple changes of heat flowdirection, an internal composite thermoelectric reinforcing circuit, aswell as an external thermoelectric reinforcing circuit for athermoelectric conversion device.

FIGS. 17 e-17 f illustrate a pair of thermoelectric elements where eachelement includes low-to-high area design, multiple changes of heat flowdirection, conjoined composite thermoelectric element design, as well asan external thermoelectric reinforcing circuit for a thermoelectricconversion device.

FIGS. 17 g illustrates a pair of thermoelectric elements where oneelement includes a n-type/p-type conjoined composite thermoelectricdesign and the other n-type element includes low-to-high area design andmultiple changes of heat flow direction.

FIG. 18 illustrates a pair of thermoelectric elements where eachthermoelectric element in the pair of elements includes a different setof design criteria for a thermoelectric conversion device.

FIG. 19 illustrates a pair of thermoelectric elements where eachthermoelectric element includes a vertical cutout at the heat outputsurface of the element to enhance the effectiveness of an externalthermoelectric reinforcing circuit for a thermoelectric conversiondevice.

FIG. 20 illustrates a pair of thermoelectric spring-like elements whereeach thermoelectric element is in the shape of a helical spring

FIG. 21 illustrates a thermoelectric element in the shape of arolled/coiled spring pin.

FIG. 22 illustrates a top view of a thermoelectric element pair in thecombined shape of a helical spring and rolled/coiled spring pin.

FIG. 23 illustrates the setup used for comparison testing the designcriteria performance of the thermoelectric element pairs.

DETAILED DESCRIPTION

The conversion efficiency of heat to useful energy is an on-goingchallenge for the energy industry. Current commercially availablethermoelectric conversion devices, for cooling and power generation, arefabricated from regular-shaped (rectangular, cube, cylindrical, etc.)thermoelectric elements and produce relatively low efficiency heatconversion when compared to other renewable energy conversiontechnologies such as photovoltaic and wind power.

Thermoelectric conversion devices have made incremental gains in deviceefficiency over the past decade mainly due to continued development ofmany new expensive thermoelectric materials with higher ZT (athermoelectric figure of merit). Utilizing the new expensive materialsno doubt yields slightly better efficiency for the thermoelectricdevices but cost makes them prohibitive for commercial use, and they arenot yet efficiently competitive to other renewable energy conversiontechnologies, such as photovoltaic.

Other types of thermoelectric conversion devices include otherfabrication techniques including vapor deposition, thin-film, design/layout on an electronic material wafer, segmented design, nanomaterials,nanotube devices, etc., that also incrementally help in surmounting thethermoelectric efficiency barrier; however, the fabrication costs toproduce them still remain prohibitively high.

The basic premise of the workings of a thermoelectric device is that thetemperature gradient/difference from hot side of a thermoelectricelement pair (1) to the cold side of element pair (2) determines thevoltage across the device and hence the efficiency. Therefore,tremendous effort continues to be expended in the development of heatsink/cooling assemblies that rapidly remove the heat expended from thecold side of the element as well as new thermoelectric materials thatprovide more favorable thermoelectric output properties.

Commercially available conventional thermoelectric conversion devicesrequire an n-type thermoelectric element as well as a p-typethermoelectric element, both fabricated from standard relativelyinexpensive bulk materials, which are interconnected. FIG. 1 providesthe general layout of a typical commercially available thermoelectricdevice. N-type and p-type Bismuth Telluride [(Bi Sb)₂Te₃] thermoelectricelements, mostly rectangular in shape, i.e., the cross-sectional area isconstant along the vertical axis or path of heat flow, are sandwichedbetween two high thermal conductivity alumina substrates. Withalternating bottom interconnects (3) and top interconnects (4), then-type and p-type elements are connected sequentially in series. For thedrawings of this patent, the heat flow is from the bottom to the top,making all thermoelectric elements thermally in parallel. In coolingmode, an externally applied current forces the heat to flow from thebottom to the top. In power generation mode, heat flowing from thebottom to the top drives a current through an external load.

This patent incorporates new thermoelectric element designs andinterconnections that empower the element to self-regulate and improvethe temperature gradient of each thermoelectric element, enhance circuitperformance of the thermoelectric element pairs and ultimatelycontribute to the optimal output efficiency of the thermoelectricconversion device.

Low-Area Heat Input to High-Area Heat Output: This design requires theheat output surface area, in contact with cooling plate/source, of eachelement to be greater than the heat input surface area, in contact withthe heating plate/source, of each element (FIG. 2). Thus, since theElement Area_(Cool) >Element Area_(Hot) during normal operatingconditions, the temperature at the cool end of the element is lowered,the heat flow in the element is better controlled and temperaturegradient regulation is performed by the internal workings of thethermoelectric elements. Accordingly, since the exit temperature for themodified thermoelectric element is lowered as compared to that of aconventional/rectangular thermoelectric element, this results in thefollowing:

-   greater temperature gradient for the modified thermoelectric    element/device-   increase in conversion efficiency for modified thermoelectric    element/device-   lowering the requirement for external removal of heat, and-   the electricity required to perform comparative cooling is also    lowered.

Changes in Heat Flow Direction(s): This design treats the action of heatflowing through the thermoelectric elements as if it were fluid. Theproposed modified designs channel the heat in varying directions whileflowing through the element (FIG. 3). The changes in heat flowdirections are created by making horizontal cutouts (6) and/or verticalcutouts (7), made at any angle, and/or central holes (8) in the standardrectangular thermoelectric elements.

An additional design to assist in channeling heat flowing through theelement is a conjoined composite thermoelectric element. This designincludes a multi-directional thermoelectric element of, say n-typematerial, designed with an additional “branch” of paired, say p-type,element attached close to the base/heat input area of the main elementpart (FIGS. 17 e-17 g). Introduction of thermal and/or electricalinsulation between the branch and the multi-directional main elementpart could be beneficial to improving performance of the conjoinedcomposite thermoelectric element. This element design performs best whenused as a conjoined element pair (FIGS. 17 e-17 f) or with a change inn-type and p-type alternating element array (FIG. 17 g), both of theaforementioned used with an optional external reinforcing circuit (Para0044).

The changes in heat flow direction effectively better excite andactivate electrical activity across the entire cross-sectional area ofall points internal to the thermoelectric element that would normallyremain relatively dormant. Multiple changes in heat flow directions ineach thermoelectric element have demonstrated better results. Also, thiscriterion will produce more compact designs of thermoelectric conversiondevices.

Fabrication of the modified thermoelectric elements can be accomplishedby extruding the raw element material to net shape, including as many ofthe described criteria into the extruded shape, and slice/dice theextrusion to the desired thickness.

The use of a helical spring element design (10) provides infinite,continuous changes in the heat flow direction. Each such thermoelectric(n-type or p-type) element can be made in a helical coiled spring form(FIG. 20) or a thermoelectric element can be fabricated like acoiled/rolled spring pin by rolling an insulator sheet between thelayers of an n-type or p-type sheet (FIG. 21). The ideal design for sucha spring-like thermoelectric element pair includes a combination ofhelical spring and a coiled/rolled spring pin whereby insulator tapesare rolled between the layers of n-type and p-type thermoelectricelement tapes to form a helical spring shaped thermoelectric elementpair (FIG. 22). In addition, a core material placed at center of thespring-like thermoelectric elements or element pairs will providefurther enhancement to the temperature gradient and overall efficiencyof the thermoelectric element pairs.

In addition, a simple helical shaped hollow container, single or doublebarreled and made from plastic or other insulator material will alsosuffice; the container(s) is/are filled with thermoelectric fluid andcapped at both ends with conductive closures to complete thethermoelectric elements or element pairs ready for use in athermoelectric device. The spring-like thermoelectric elements/pairswill yield a more efficient and more compact thermoelectric conversiondevice.

Thermoelectric Reinforcing Circuits: The designs of two uniquethermoelectric reinforcing circuits, internal change of layout forthermoelectric elements and external interconnection for thermoelectricelement pairs, are presented in this patent. Both designs intensify theinner workings of the thermoelectric element to significantly increasethe output efficiency of thermoelectric conversion devices.

The internal thermoelectric reinforcing circuit (9) includes one or moreextra loop(s) of say n-type material that is/are connected to the p-typematerial element, and vice versa, to create a composite element; theloop (FIGS. 17 a-17 b) may be attached with thermally-electricallyconductive adhesive or by other means. The thermoelectric reinforcingloop/circuit enhances the performance of the composite thermoelectricelement.

The external thermoelectric reinforcing circuit (5) includes anadditional connection made between the elements of a thermoelectricelement pair, i.e., if the standard connection between the elements of athermoelectric element pair is at the bottom, as described in Para.0032, the additional external thermoelectric reinforcing circuitconnection is made at the top of and between the same thermoelectricelement pair. For best results, the external thermoelectric reinforcingcircuit connection can be alternated at top as described above, thusrepeated for each thermoelectric element pair in the thermoelectricdevice circuit.

When used internally, externally or combined, each thermoelectricreinforcing circuit provides the following multifunctional benefits forthe thermoelectric element/element pair:

-   it increases the temperature gradient between hot and cool ends of    each thermoelectric element to magnify the heat conversion    efficiency-   it stabilizes the heat flow to create a temperature equilibrium    between the n-type and p-type elements in the thermoelectric element    pair by transferring heat from the hotter temperature surface to the    cooler surface; this temperature equilibrium at one end of the    thermoelectric element pair produces more responsive thermoelectric    functionality between the excited/heated end and equilibrium/cooler    ends within the thermoelectric elements which yields higher    conversion efficiency-   the additional electrical circuit creates a thermoelectric cooling    effect in conjunction with the power generation of the    thermoelectric element pair; this further controls the heat flow    through the thermoelectric element pairs, thus reducing the cooling    requirement on the thermoelectric element pair and yields greater    conversion efficiency.-   it allows part of the electrical output from one thermoelectric    element to be channeled back to the other thermoelectric element in    the thermoelectric element pair that augments the electrical    performance of both thermoelectric elements, thus producing better    heat conversion efficiency for the thermoelectric element    pair/device.

Comparative Testing Performed on new Thermoelectric Device Designs:Testing was performed on thermoelectric element pairs including thevarious new designs presented above. Three batches of thermoelectricdevices were fabricated; in each batch standard elements pairs werefabricated as a reference/comparative benchmark.

Per the design criteria discussed above the following work wasperformed:

-   several thermoelectric element shapes were machined to design    requirements-   each pair of thermoelectric elements was sandwiched between alumina    plates (11) and electrical connections were made between the    thermoelectric elements specific to each thermoelectric element    pair/device, as depicted in the drawings-   each thermoelectric device was placed on a test bench as depicted in    FIG. 23-   heat was applied to the bottom alumina plate (1) of the    thermoelectric device-   heat removal/cooling was applied to the top alumina plate (2) of the    thermoelectric device-   extreme care was taken at all times to isolate the heat application    strictly to the bottom plate and the same for the cooling at the top    plate.

For each test performed on the devices fabricated, the following testcriteria were intentionally and strictly kept constant:

-   1) Electrical connections in device and circuitry-   2) Temperature of heat input (1)-   3) Heat removal/cooling (2)-   4) Test circuit layout including resistor (12), wires and voltmeter    (13)-   5) Alumina plates—size, thickness, material type-   6) N-type material—initial size and from same material batch-   7) P-type material—initial size and from same material batch-   8) Time of test heat up and measurement of results

Testing: Heat was applied to one side of one test device at a time andheat removal/cooling applied to the other side of the device. Thevoltage readings were recorded at 5-10 minute intervals

Test results for each of the three batches differed slightly; however,it was found that for each batch the results were comparably the same,i.e., the new thermoelectric elements/device designs produced resultsthat were 20% to 45% higher than those of the standard thermoelectricdevice designs.

Additional test observations:

-   a few of the thermoelectric element design criteria discussed above    achieved maximum or higher results much faster than the others-   increasing the rate of heat removal at the cool ends for a few of    the new thermoelectric element design criteria did not produce a    significant change in results, which leads directly to the premise    that external cooling requirements are reduced for the new designs.-   multiple thermoelectric element pair devices produced very similar    test results-   limited testing of the thermoelectric devices in cooling    demonstrated fair results.

It is anticipated that the proposed designs of this patent be utilizedwith all thermoelectric materials and fluids, element designs, elementpairs connections, device shapes, layouts and arrays, fabricationprocesses, and methods of manufacture to produce the highest efficiencythermoelectric elements, thermoelectric element pairs and thermoelectricconversion devices for economical, high conversion efficiency andemission free power generation and cooling.

Many widely different examples of this invention may be made withoutdeparting from the spirit and scope thereof, and it is to be understoodthat the invention is not limited to the specific examples thereofexcept as defined in the appended claims.

1. A heat conversion methodology to enhance the efficiency ofthermoelectric devices comprising use of modified irregular shapedthermoelectric element designs in the devices which include(s) one ormore of the following design criteria: at least one thermoelectricelement used in the thermoelectric conversion device includes heatoutput area of the thermoelectric element which is greater than the heatinput area of the thermoelectric element at least one of thethermoelectric elements in the thermoelectric conversion device includesmultiple heat output areas incorporated to the thermoelectric element.at least one thermoelectric element in the thermoelectric conversiondevice includes one or more vertical edge cutouts to provide change(s)in heat flow direction, in any axis or orientation, incorporated in thethermoelectric element at least one thermoelectric element in thethermoelectric conversion device includes one or more horizontal edgecutouts to provide change(s) in heat flow direction, in any axis ororientation, incorporated in the thermoelectric element at least onethermoelectric element in the thermoelectric conversion device includesone or more central cutouts or holes to provide change(s) in heat flowdirection, in any axis or orientation, incorporated in thethermoelectric element at least one of the thermoelectric elements in athermoelectric conversion device includes one or more conjoinedcomposite thermoelectric element(s) at least one of the thermoelectricelements in a thermoelectric conversion device includes one or moreinternal composite thermoelectric reinforcing circuit(s) that is/areincorporated to the thermoelectric element.
 2. A heat conversionmethodology whereby one or more of the thermoelectric elements/pairsused in a thermoelectric conversion device: is formed like a helicalcoil spring or coiled/rolled spring pin is formed like a combination ofa helical coil spring and coiled/rolled spring pin, includes a specialcore material, placed at center of the coiled spring-like thermoelectricelement/pair, which further enhances efficiency of the thermoelectricconversion device.
 3. A heat conversion methodology to enhance theefficiency of a thermoelectric conversion device wherein at least onepair of the thermoelectric elements used in the thermoelectric deviceincludes an external thermoelectric reinforcing circuit incorporated tothe element pair in the thermoelectric device.
 4. The method of claim 1,2, or 3 wherein the modified irregular shaped thermoelectric elementused in the thermoelectric conversion device is fabricated from athermoelectric material.
 5. The method of claim 1, 2, or 3 wherein themodified irregular shaped thermoelectric element used in thethermoelectric conversion device is fabricated from a shaped hollowcontainer of electrical insulator material with conductive end closuresand is filled with a thermoelectric fluid.
 6. The method of claim 1, 2,or 3 wherein the modified irregular shaped thermoelectric element(s)used in a thermoelectric conversion device is (are) fabricated by anyfabrication process or method.
 7. The method of claim 1, 2, or 3 whereinat least one of the thermoelectric element pairs used in athermoelectric conversion device includes an n-type element in theelement pair having one set of design criteria and a p-type element inthe thermoelectric element pair having a different set of designcriteria.
 8. The method of claim 1, 2 or 3 wherein each modifiedirregular shaped thermoelectric element can be placed at any anglerelative to the mounting surface of the thermoelectric conversiondevice.
 9. The method of claim 3 whereby the external thermoelectricreinforcing circuit incorporated to the element pair in thethermoelectric conversion device has multiple external thermoelectriccircuit connections from one type (say, n-type) of thermoelectricelement in the element pair to the other type (say, p-type) ofthermoelectric elements surrounding the first (n-type) thermoelectricelement of the element array in the thermoelectric conversion device.